Abstract
In 1999, the Maridal concrete culvert was built in Oslo, Norway. Natural aggregates known to be moderately alkali reactive according to laboratory and field experience were used. Field survey combined with microstructural analyses of drilled cores have confirmed that the use of OPC with relatively low alkali content (0.53 % Na2O eq.) combined with addition of 5% silica fume have prevented development of ASR. By corresponding field survey and microstructural analyses, it has also been verified that a similar aggregate combination has caused ASR in the nearby Storo bridge which was built in 1994. 18 years of service is too short time to conclude whether the concrete composition used in the Maridal culvert has a potential to develop ASR or not. To assess the long-term potential of ASR, residual expansion testing was performed. The conclusion from this testing is that the potential for further reaction and expansion is limited.